Electrical connector



Aug' 25, 1947 B. A. BELs 2,426,429

ELECTRICAL CONNECTOR Filed Jan. 6, 1945 2 sheets-sheet' 1 FIG.3a

INVENTOR. BASIL A. BELS ATTORNEY B. A. BELS ELECTRICAL CONNECTOR Aug. 26, 1947. Y

2 Sheets-Sheet 2 Filed Jan. 6, 1945 INVENTOR. BAS". A. W

BELS

Patented Aug. 26, 1947 ELECTRICAL CGNNECTOR Basil A. Bels, Great Neck, N. Y., assignor, by

mesne assignments, to Hazeltine Research Inc., Chicago, Ill., a corporation of Illinois Application January 6, 1945, Serial No. 571,610

11 Claims.

'I'he present'` invention relates to electrical connectors and, particularly, to such connectors which are adapted to engage an approximately cylindrical conductive contact member. While the invention is of general application, it has particular utility as an electrode-terminal connector for use with vacuum tubes of the type having an electrode terminal sealed through, or directly supported by, a wall of an evacuated glass envelope and will be described in that con nection.

It frequently is desirable to provide an electrical connector adapted to engage an approxi mately cylindrical conductive contact member.

No essential problem is encountered in a sim` ple connector of this type when the only requirement to be met is that of providing a positive consistent electrical contact with the contact member. However, problems of design arise when the connector must additionally provide adequate and consistent thermal contact with the contact member, to enable substantial conduction of thermal energy there-between and particularly is this true when the force required to eiiect complete engagement between the contact member and the connector must be minimized, The problems thus raised are multiplied where the connector must at the same time allow for some eccentricity of the contact member and for lateral and angular departures from coincidence of the axes of the contact member and connector.

To illustrate by example the problems encountered in providing an electrical connector of the type described, consider the case of an electrical connector for a vacuum tube of the type having an anode terminal sealed through or supported by one wall of a glass envelope. The power handled by the tube may be sufficiently large that the anode terminal heats so excessively as to fracture the glass seal unless precautions are taken to conduct thermal energy rapidly away vfrom the anode terminal. The anode-terminal connector in such oase must not only provide the required electrical con-- nection to the anode terminal, but additionally must rmly engage most of the Asurface of the latter and be capable of furnishing a path of low thermal resistance to a thermal-dissipative surface if adequate cooling of the anode terminal is to be effected. This usually presents no undue problem if the anode connector is of split construction adapted to be placed over the anode terminal and clamped thereto. Where, however, it is required that the anode connector be simply slipped bodily over the anode terminal without subsequent clamping, serious problems arise concerning the manner of attaining the required firm thermal contact over a large contact area particularly since the force required to effect complete engagement of the connector and terminal cannot be large without danger of fracture of the tube glass envelope.

In many such applications, it is further necessary that the vacuum tube be physically inserted axially into operative position and that, during such insertion, the anode terminal and possibly one or more electrode terminals fully engage xed electrical connectors provided therefor. The anode terminal in these tubes usually is positioned axially of thetube envelope at the inserted end thereof. It is quite difficult in practice accurately tc center and axially to align the anode terminal at the time it is sealed to the glass envelope of the tube. The anode-terminal connector consequently must additionally be capable of permitting small lateral and angular departures from coincidence of the axes of the terminal and connector Without placing undue strain on the terminal since this strain would be transmitted directly to the glass seal and would tend to fracture it.

It is an object of the present invention therefore to provide a new and improved electrical connector adapted to engage an approximately cylindrical conductive contact member.

It is a further object of the invention to provide a new and improved electrical connector, adapted to engage an approximately cylindrical conductive contact member, having greater thermal conductivity than has readily been heretofore obtainable in a connector of the type deber with the connector while, at the same time,

permitting relative lateral and angular departures from coincidence of the axes of the contact member and connector.

f resonator In accordance with the invention, an electrical connector adapted to engage an approximately cylindrical conductive contact member comprises a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact fingers positioned internally of the element but resiliently connected at one extremity thereto and extending inwardly from the element radially with respect to the axis of the element. Each oi the contact ngers has two relatively rigid linear portions connected at one end by a resilient portion to provide for each such finger a V-shaped cross-sectional configuration at its intersection with a plane which includes the axis of the aforementioned cylindrical element. The radial dimensions of the element are so selected with relation to the diameter of the contact member that`the innermost linear portions of the Contact ngers are .adapted to make consistent and substantially uniform electrical and thermal Contact with the contact member along a substantial portion of their lengths while at the same time the contact iingers permit relative departures from coincidence of the axes of the element and of the contact member and minimize the force required to effect complete engagement of the Contact member with the connector.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed 'out in the appended claims.

Referring now to the drawings, Fig. 1 illustrates a high-frequency wave-signal oscillator which utilizes electrical connectors embodying the present invention; Fig. 2 is an enlarged crosssectional view of one form of electrical connector of the present invention; Figs. 3a, 3b and 3c illustrate certainsteps employed in one l'method of forming the electrical connector of the invention; Fig. 4 illustrates a second method of forming the electrical connector; Figs. 5a. and

5b illustrate an electrical connector embodying the invention formed by a machining process; and Fig. 6 illustrates a portion of an electrical connector embodying a modified form of the invention.

Referring now more particularly. to Fig. 1 of the drawings, there is illustrated a high-frequency wave-signal oscillator which utilizes electrical connectors embodying the present invention. This oscillator is disclosed and claimed in -a copending application of Harold A. Wheeler, entitled Wave-signal translating device, Serial No. 565,828, led November 30, 1944, and assigned to the same assignee as the present application. Reference is made to this copending application for a detailed description of the oscillator and its mode of operation. Briefly, the oscillator includes a rst or anode cavity IU and a second or cathode cavity resonator I I which is capacitively coupled to the resonator IIJ by a probe I2 arranged to extend 'through an aperture I3 in a diaphragm I4 separating the cavity resonators IIJ and Il. The cavity resonator I0 includes a cylindrical hollow outer conductor I5 and a cylindrical hollow inner conductor I6 which are maintained in iixed coaxial relationship by insulating spacers I'I secured between the conductors I5 and I6 at points suitably spaced around the circumference thereoi'. One end of the inner conductor IB is closed by a disc I3 having a centrally positioned co- 4 axial aperture I9 in which is secured by a pressed t or other suitable means an electrical connector 20 embodying the present invention and presently to be described in greater detail. The outer conductor I5 of the cavity resonator I0 is closed at its end opposite the diaphragm I4 by a disc ZI which supports, in coaxial relation with the conductor I5, a cylindrical conductor 22 'of diameter appreciably smaller than that of the inner conductor I6. The conductor 22 effectively forms a re-entrant portion of the outer conductor I5 and is used for purposes of tuning this resonator I0.

The second or cathode'resonator II similarly includes an outer hollow cylindrical conductor I5, which may be an extension of the conductor I5, and an inner hollow cylindrical conductor 2:3 which is supported by a conductive ring 2li in coaxial relation with the outer conductor I5. A conductive ring 25 is positioned between and electrically engages the inner and outer conductors 23 and I5', this ring being adjustable axially along these conductors for purposes of tuning the cathode cavity resonator. The end of the inner conductor 23 adjacent the diaphragm I4 is closed by a disc 25 having a cen trally positioned coaxial aperture in whicn is secured an electrical connector 2l having a construction similar to that of the electrical connector 20. The diaphragm I4 likewise has a centrally positioned coaxial aperture in which is secured an' electrical connector 28 also embodying a construction similar to that of the electrical connector 20.

A vacuum tube 294mg an approximately cylindrical conductive contact member or anode terminal 33 hermetically sealed to one end of a cylindrical glass envelope portion 3|, a conductive grid disc 32 which is hermetically sealed between the envelope portion 3l and a second cylindrical glass envelope portion 33, and a conductive cathode terminal 34 sealed to one end of the glass envelope portion 33. The tube 29 is insertable axially through the center of the hollow conductor 23 of the cathode cavity resonator II into operative position with its anode terminal 30 engaging the electrical connnector 20, its grid Aterminal disc 32 engaging the electrical connector 28 and its cathode terminal 34 engaging the electrical connector 21. For purposes of simplicity, certain electrical connectors which extend out of the Iiat base of the tube 29 are not shown nor is the means shown for maintaining tube 29 in the op erative position described.

Reference is made to the aforementioned copending Wheeler application for a detailed description of the oscillator described. Briefly considered, oscillations developed in the cathode cavity resonator I I are repeated by the vacuum tube 29 to the anode cavity resonator Il) and a portion of the oscillatory energy developed in the latter is applied by the probe I2 back to the cathode cavity resonator II to maintain sustained oscillation of the oscillator.

During operation of the oscillator, it is necessary that the anode terminal 3|] of the tube 23 be electrically connected by the electrical connector 2Il` through the disc I8 and the inner conductor I6 of the anode cavity resonator I0 to a source of anode potential indicated as +B. The vacuum tube 29 during operation translates suiTicient power that the temperature of the anode terminal 30 is raised to a high value. There is consequently danger of fracturing the glass seal between the anode terminal 3U and the tube envelope portion 3| unless thermal energy is conducted rapidly away from the anode terminal. Hence, it is necessary that the electrical connector 2li make good thermal contact with the anode terminal 30 over a major portion of the surface of the latter and that the connector provide a path of goodthermal conductivity to the disc I8 and the conductor I6 in order that the latter elements may act as thermal radiators to maintain the anode terminal .30 at a relatively low safe temperature.

An additional requirement of the electrical counector 20 is that it must accommodate eccentricities of the anode terminal 30 and permit relative departures from coincidence of the axes of the anode terminal and the connector while the vacuum tube 23 is in its operative position in the oscillator and also during insertion and withdrawal thereof. Otherwise a mechanical strain is placed upon the anode terminal 30 which may fracture the seal between the anode terminal and the tube envelope portion 3|. For a like reason, the electrical vconnector 20 must minimize the force required to effect complete engagement andy disengagementof the anode terminal 30 with the connector.

Certain of the requirements last mentioned with relationl to the electrical connector 20 apply, though to a lesser degree, to the electrical connectors 21 and 28.

Considering now in greater particularity the 6 i forming the electrical connector 20. As shown in the plan View of Fig. 3a, an elongated strip of conductive sheet material 39, which may, for example, be beryllium copper, is first serrated along a longitudinal edge to provide a plurality of sei-rations 40. The shape of the serrations shown permits the material 39 to be rolled into a cylindrical configuration after the contact fingers have been formed in a manner presently to be described, Either before or after forming the serrations, a longitudinal groove 4|, shown more clearly in the end view of Fig. 3b, is preferably rolled into the material 39 on one side thereof along the roots of the serrations and a similar.

longitudinal groove 42 is rolled into the opposite side of material 39 at a region spaced from the rst groove 4I toward the ends of the serrations.

' vide the electrical connector shown in Fig. 2, the

portion of the oscillator arrangement described as heretofore explained is adapted to engage the approximately cylindrical conductive Contact member 30, includes a. relatively rigid cylindrical element of conductive material, for example, beryllium copper, and a plurality of conductive resilient contact fingers 36 resiliently connected at one extremity 31 to one edge of the element 35 and extending inwardly from the latter radially with respect to the axis of the element. As shown, the contact iingers 36 are connected to the upper edge of the element 35 and are arched toward the lower edge of this element, each of the ngers having a V-shaped cross-sectional conguration at its intersection with a plane which includes the axis of the element 35. Further, each of these fingers has two relatively rigid linear portions 36a, 36o, which are connected at one end by a resilient portion 38. These Contact ngers provide a, substantially continuous laminated cylindrical contact surface symmetrical with relation to the axis of the element 35.-

IThe radial dimensions of the element 35 are so selected with relation to the diameter of the contact member with which the electrical connector is to be used that the innermost linear portions 36h of the contact lingers 3E are adapted to make consistent and substantially uniform electrical and thermal contact with the contact member along their lengths, as shown more clearly in Fig. l, while at the same time the contact ngers permit relative departures from coin-` cidence of the axes of the element 35 and the contact member and minimize the force required to effect complete engagement of the contact member with the connector 20. Fig. `1 illustrates the manner in which the contact finger portions 36a y ends of the unserrated portion of the material 39 then being in abutting relation. The forming preferably is accomplished by using several flat templates of relatively thick stock material.

- These templates have turned into one face thereof a cylindrical groove of width only wide enough to receive the unserrated portion of the mateial 39 and a concentric groove formed radiallyinside of the rst groove and of a width to accommodate the contact fingers 36. The diameters of these grooves are relatively large for the first template and become progressively smaller for successivetemplates until the last template has grooves of diameter equal to that which the finished connector is to have. Starting with the structure of Fig. 3c, the unserrated portion of the material 39 is pressed, starting at one end of the material, into the cylindrical grooves of that template having the largest diameter grooves. 'I'his causes the unserrated portion of the material 39 to, take a permanent cylindrical set or deformation. By repeating this process using successive templates of smaller groove diameter, the electrical connector is ultimately formed to have the cylindrical configuration of Fig. 2.

Fig. 4 represents an additional method of forming an electrical connector embodying the present invention. Here the connector is formed from a hollow cylinder 43 of conductive material, for example, beryllium copper, serrated at one end to provide the serrations d4 having a shape similar to the serrations di) of Fig. 3a. A. groove 45 is rolled or otherwise suitably formed on the inside of the cylinder d3 at the roots of the serrations lit while a groove d@ is rolled or otherwise suitably formed on the exterior surface of the cylinder 33 approximately at the midpoint of the serrations A4. Each of the ser.- rations lid is then bentoutwardly and back upon itself at the groove 36, as indicated by the brokenline arrow' I, and each serration is then bent inwardly of the cylinder 43 at the inner groove' t5, as vindicated by the broken-line arrow II, to

t provide the electrical connector shown in Fig. 2,

li'romv the foregoing description of the Fig. i method of forming the electrical connector, it will be apparent that yet another method is to use a serrated, grooved, flat stock as in Fig. 3a, to roll this nat, stock into the cylindrical coniiguration of Fig. 4, and then to proceed as described in connection with the latter gure.

An additional method of forming the electrical connector of the present invention is illustrated by the cross-sectional side view of Fig. a and the top view of Fig. 5b. Here a circular piece of conductive material 41 has a concentric groove 48 machined into one surface thereof, a similar concentric groove y49 machined into its opposite face, and a tapered centrally machined bore 5D. The grooves 48, 49 and the bore 5|) has a contour such as to provide the desired V-shaped cross'- `sectional. configuration of the contact fingers. The central portion of the material 4l -is then slotted radially with respect to its axis to provide a plurality of resilient contact lingers 5l. Suitable mounting holes 52 may be drilled or otherwise formed in the material 41 if desired.

For some applications of the electrical con nectr of the present invention, it may be desirable to employ a soft copper for the material .oi the connector and to use additionall means by i which to bias the contact fingers of the connector radially inwardly of the connector to provide the required electrical a`nd thermal contact with a contact member. Fig.I 6 illustrates an electrical connector 20 similarto that of Fig. 2 and represents a. modification of the invention of the type last mentioned. Elements of Fig. 6 corresponding to similar elements of Fig. 2 are designated by similar reference numerals. In this modiiication, the outside surface of the inner linear portion 36D of the contact iingers 36 is grooved, in a plane normal to the axis of the electrical connector 20, to receive a spring-steel split ring 53. The split ring 53 thus encircles a portion of the contact lingers and biases the contact fingers radially toward the axis of the electrical connector. The `advantage of using soft copper in the electrical connector, in preference to beryllium copper, for example, lies in the fact iat the heat conductivity of soft copper is greater thus permitting a greater transfer of thermal energy between the electrical connector and the contact member used therewith.

yIt will be apparent from the above description of the invention that an electrical connector embodying the invention insures positive, consistent and substantially uniform electrical and thermal contact with a cylindrical conductive contact member while minimizing the force required to effect complete engagement of the contact member with the connector. At the same time, the electrical connector of thel present invention permits relative lateral and angular de partures from coincidence of the axes oi the contact member and connector. The electrical connector of the present invention has the additional advantage that it provides much higher thermal conductivity than has readily been heretoforc obtainable in a connector of this type and yet the connector is of simplied, improved and relatively inexpensive construction.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modi fications may be made therein Without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is: l

l. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact fingers positioned internally of said element but resiliently connected at one extremity theretoand extending inwardly -from said element radially with respect to the axis of said element, each of said fingers having two relatively rigid linear portions connected at one end by a resilient portion to provide for said each finger a V-shaped cross-sectional configuration at its intersection with a plane which includes said axis, the radial dimensions of said element being so selected with relation to the diameter of said contact member that the innermost linear portions of said contact lingers are adapted tofmake consistent and substantially uniform electrical and thermal contact with said Contact member along a substantial portion of their lengths While at the same time said contact ngers permit relative departures from coincidence of the axes of said element and said contact member andminimize the force required to eiect complete engagement of said contact member with said connector.

2. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact lingers positioned internally of said element but resiliently connected at one extremity thereto and extending inwardly from said element radially with respect to the axis of said element to provide a substantially continuous laminated cylindrical contact surface symmetrical with relation to said axis, each of said fingers having two relatively rigid linear portions connected at one end by a resilient portion to provide for said each finger a V shaped cross-sectional configuration 4at its intersection with a plane which includes said axis, the radial dimensions of said element being so selected with relation to the diameter of said contact member that the innermost linear portions of said contact fingers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said contact iingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said contact member with said connector.

3. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact fingers positioned internally of said element but resiliently connected at one extremity to one edge of said element and extending inwardly from said element radially with respect to the axis of said element, each of said fingers having two relatively rigid linear portions connected at one end by a resilient portion to provide for said each finger a V-shaped cross-sectional configuration at its intersection with a plane which includes said axis, the radial dimensions of said element being so selected with relation to the diameter of said contact member that the innermost linear portions of said contact fingers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said contact fingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said contact member with said connector.

4. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact fingers positioned internally of said element but resiliently connected at one extremity to one edge of said element and extending inwardly from said element radially with respect to the axis of said element with said fingers arched toward the other edge of said element, each of said fingers having two relatively rigid linear portions connected at one end by a resilient portion to provide for said each finger a V-shaped cross-sectional configuration at its intersection with a Iplane which includes said axis, the radial -dimensions of said element being s selected with relation to the diameter of said contact member that the innermost linear portions of said contact fingers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said contact iingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said` contact member with said connector.

5. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, ai relatively rigid cylindrical element of conductiv e, material having a plurality of resilient conductive finger serrations at one edge of said element; said finger serrations extending inwardiy from said element approximatelyat the roots of said serrations and having a reverse bend at an intermediate point along their lengthto provide ngers each having a V-shaped. cross-sectional conguration at its intersection with a plane which includes the axis of said element and extending. radially with lrespect to said axis, the radial dimensions of said element being so selected vwith relation to the diameter of said contact member that the innermost linear portions of said Contact lingers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said contact fingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said Contact member with said connector.

6. An electrical lconnector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material having a circunim ferential groove on its inner side spaced from one end thereof to provide yan area of increased resilience and a plurality of contact finger serrations atthe opposite end of said element and extending into said groove, said finger serrations extending inwardly at said groove radially with respect to the axis of said element, said fingers .having a groove spaced from one end thereof to provide an area of increased resilience and having a reverse bend at the said last-mentioned groove to provide fingers each having a V-shaped crosssectional conguration at its intersection with a plane which includes said axis, the radial dimensions of said element being so selected with relation to the diameter of said ,Contact member that the innermost linear portions of said contact l fingers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said Contact fingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required` to effect complete engagement of said contact member with said connector.

7. An electrical connector adapted to engage an approximately cylindrical conductive Contact member comprising, a relatively rigid cylindrical element of conductive material having a circumferential rolled groove therein on its inner side spaced from one end thereof to provide an area of increased resilience and a plurality or" Contact finger serrations at the opposite end of said element extending inwardly at said groove radially with respect to the axis of said element, each of said lingers having a rolled groove at a region spaced from one end thereof to provide an area of increased resilience and having a reverse bend at said last-mentioned groove to provide for each said nger a V-shaped cross-sectional configuration at its intersection with a plane which inciudes said axis, the radial dimensions of said element being so selected with relation-to the diameter of said contact member that the innermost linear portions of said contact ngers are adapted to make consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths While at the same time said contact fingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said contact member with said connector.

8. An Aelectrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient contact iingers connected at one extremity thereto and extending inwardly from said element radially with respect to the axis of said element, each of said fingers having a V-shaped cross-sectional configuration at its intersection with a plane which includes said axis, spring means for biasing said contact ngers radially toward said axis to increase the Contact pressure 'of said ngers on said contact member during engagement of said contact member and said connector, the radial dimensionsof said element being so selected with relation to the diameter of said Contact member that the innermost linear portions of said contact fingers are adapted to malte consistent and substantially uniform electrical and thermal contact with said contact member along a substantial portion of their lengths while at the same time said Contact iingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagementA of said contact member with said connector.

9. An electrical connector adapted to engage an approximately cylindrical conductive contact member comprising, a relatively rigid cylindrical 11 element of conductive material and a plurality of conductive resilient contact lingers connected at one extremity thereto and extending inwardly from said element radially with respect to the axis of said element, each of said lingers having a V-shaped cross-sectional configuration at its intersection with a plane which includes said axis, a split ring spring member encircling said contact fingers for biasing said contact fingers radially toward said axis to increase the contact pressure of said fingers on said contact member during engagement of said contact member and said connector, the radial dimensions of said element being so selected with relation to the diameter of said Contact member that the innermost linear portions of said contact iingers are adapted to make consistent and substantially uniform electrigal and thermal contact with said contact member along a substantial portion of their lengths While at the same time said Contact fingers permit relative departures from coincidence of the axes of said element and said contact member and minimize the force required to effect complete engagement of said contact member with said connector.

l0. The method of fabricating an electrical connector adapted -to engage an approximately cylindrical conductive Contact member which comprises the steps of serrating along a longitudinal edge an elongated strip oiv conductive sheet material, forming a longitudinal groove in said material on one side thereof along the roots oi said serrations and forming a longitudinal groove on the opposite side of said material in a region vspaced from said iirst groove toward the ends of said serrations, bending said serrations back upon said material .at said first groove and on the side thereof of said first groove, bending the end portion of each of said serrations back upon said each serration at said second groove and on the side thereof said second groove, and bending the unserrated portion of said material into a cylinder with said serrations extending inwardly radially of the axis of said cylinder to vprovide a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient V-shaped con- 12 4 tact lingers connected at one extremity to one edge of said element and extending inwardly from said element radially with respect to the axis thereof and arched toward the other edge of said element.

11. A method of fabricating an electrical connector adapted to engage an approximately cy lindrical conductive contact member which comprises the steps of serrating along a longitudil0 nal edge an elongated strip of conductive sheet material, rolling a longitudinal groove in said material on one side thereof along the roots of said serrations and rolling a longitudinal groove on the opposite side of said material in a region 15 spaced from said first groove toward the ends of said serrations, bending said serrations back upon said material at said first groove and on the side thereof of said first groove, bending the end portion of each of said serrations back upon 20, said each serration at said second groove and on the side thereof of said second groove, and

bending the unserrated portion of said material into a cylinder with said serrations extending inwardly radially of the axis of said cylinder to provide a relatively rigid cylindrical element of conductive material and a plurality of conductive resilient V-shaped contact fingers connected at one extremity to one edge of said element and extending inwardly from said element radially with respect to the axis thereof and arched toward the other edge of said element.

BASIL A. BELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

